焊接接头的应力腐蚀开裂及防护

应力腐蚀断裂是焊接结构断裂失效的重要原因之一,这种断裂失效呈脆断特点,易导致灾难性后果.探讨应力腐蚀裂纹的产生、开裂的机理及其影响因素,并提出控制焊接结构发生应力腐蚀断裂的措施.     

Finite element model for linear-elastic mixed mode loading using adaptive mesh strategy

An adaptive mesh finite element model has been developed to predict the crack propagation direction as well as to calculate the stress intensity factors （SIFs）, under linear-elastic assumption for mixed mode loading application. The finite element mesh is generated using the advancing front method. In order to suit the requirements of the fracture analysis, the generation of the background mesh and the construction of singular elements have been added to the developed program. The adaptive remeshing process is carried out based on the posteriori stress error norm scheme to obtain an optimal mesh. Previous works of the authors have proposed techniques for adaptive mesh generation of 2D cracked models. Facilitated by the singular elements, the displacement extrapolation technique is employed to calculate the SIK The fracture is modeled by the splitting node approach and the trajectory follows the successive linear extensions of each crack increment. The SlFs values for two different case studies were estimated and validated by direct comparisons with other researchers work.     

锥杆中应力波传播的放大特性

从变截面杆中一维应力平面波的无量纲控制方程组出发,采用特征线数值解法分析了应力波在锥形杆段中的传播特性,讨论了无量纲参数λ、τ_r和R对透射波放大系数和波形的影响,为应力波放大器的合理设计提供了理论依据。在Hopkinson压杆装置上对锥杆中的应力波传播进行了实验研究。理论分析计算和实验研究结果一致地表明原先由Leftheris提出的计算公式和有关结论是错误的。     

A first order system model of fracture healing

INTRODUCTION Fracture healing is an important research subject in biomechanics. During the last years, many theories and simulation models have been proposed for de- veloping a comprehensive view of the mechanisms controlling bone morphogenesis. Pauwels (1960) was one of the first authors to propose a theory of tissue differentiation in response to local mechanical stress and strain. He assumed that deviatoric stresses com- prise the specific stimulus for the formation of fibrous connecti…     

择业期内大学生应对方式与心理健康的相关研究

目的探讨择业期内大学生应对方式与心理健康之间的相关性及其应对方式的特点;方法：采取应对方式问卷和症状自评量表对山西省境内三所高校随机抽取的120名应届本科大学生进行测评;结果：不同应对方式的选择对择业期内大学生的心理健康水平有明显的影响,其中“求助”这一应对方式可有效地帮助大学生调节心理健康水平,“自责”“退避”“合理化”三项因子和心理健康呈明显负相关;结论：择业期内大学生合理选择应对方式对保持心理健康有重要意义。     

应用网络虚拟实验技术实现压力容器应力测试实验

随着计算机技术的发展,网络虚拟实验室技术正在悄然兴起,能够实现跨时空、跨学科的仪器设备远程共享,甚至远程控制,满足科研教学对分布式实验系统的要求,本文介绍了压力容器应力测试虚拟实验的实现技术,通过计算机网络系统,研究人员或学生将不受时空的限制,随时随地与同行协作,共享仪器设备,共享数据和计算资源。     

理中丸增强机体抗寒与抗疲劳能力的实验研究

采用抗疲劳实验、耐缺氧实验、耐寒实验,测试理中丸对小鼠应激能力的影响。通过对小鼠进行抗疲劳、耐缺氧、耐寒等实验研究,论证理中丸抗寒、抗疲劳作用的有效性并对其作用机制进行初步探讨。结果显示,理中丸高、中剂量组对于小鼠游泳时间具有延长作用,对耐缺氧能力无显著作用。理中丸低、中、高剂量组小鼠耐寒实验结果显示存活率明显多于对照组,理中丸低、中、高剂量组小鼠脾细胞数和IL-2数优于对照组。研究认为：理中丸具有一定增强小鼠抗寒、抗疲劳能力,增强抗寒能力作用机制可能与增强脾脏功能,促进IL-2水平等免疫调节机制有关。     

A text classification approach to detect psychological stress combining a lexicon-based feature framework with distributional representations

Nowadays, stress has become a growing problem for society due to its high impact on individuals but also on health care systems and companies. In order to overcome this problem, early detection of stress is a key factor. Previous studies have shown the effectiveness of text analysis in the detection of sentiment, emotion, and mental illness. However, existing solutions for stress detection from text are focused on a specific corpus. There is still a lack of well-validated methods that provide good results in different datasets. We aim to advance state of the art by proposing a method to detect stress in textual data and evaluating it using multiple public English datasets. The proposed approach combines lexicon-based features with distributional representations to enhance classification performance. To help organize features for stress detection in text, we propose a lexicon-based feature framework that exploits affective, syntactic, social, and topic-related features. Also, three different word embedding techniques are studied for exploiting distributional representation. Our approach has been implemented with three machine learning models that have been evaluated in terms of performance through several experiments. This evaluation has been conducted using three public English datasets and provides a baseline for other researchers. The obtained results identify the combination of FastText embeddings with a selection of lexicon-based features as the best-performing model, achieving F-scores above 80%.     

Disparate plasma cortisol concentrations in sexually abused female children from Johannesburg,South Africa

A growing body of research indicates that a bidirectional response to a stressor may occur in maltreated children and may be associated with later life psychopathology. However, few studies have investigated stress reactivity in children when they first present to a sexual abuse clinic. Thus, in order to evaluate whether HPA axis dysregulation would be evident at first presentation to a sexual abuse clinic in young girls (n = 26), between the ages of 6–12 years old, blood samples were obtained immediately following examination at a forensic sexual abuse clinic and from the matched control group of children (n = 14; 10.1 ± 0.8) immediately following a bone density scan. Stratification of the sexually abused group into those children who were reportedly abused by a stranger and had no other family stressors (n = 15, 10.4 ± 1.8) and those children whose parents reported abuse of the child by a stranger and other family stressors (n = 11; 9.5 ± 1.8) revealed differences in stress reactivity. Plasma concentrations, of the children from the forensic clinic, were significantly increased in children who reported abuse by a stranger only (322.3 ± 117.4 nmol/l) and significantly decreased in children whose histories indicated sexual abuse by a stranger and other family stressors (149.6 ± 39.7 nmol/l) when compared to the control group (225.5 ± 47.5 nmol/l). In conclusion, following sexual abuse and a secondary stressor, the forensic examination, there is evidence of divergent cortisol responses in the stratified clinical group of children.